////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2009 Daniel F. Hanson
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
////////////////////////////////////////////////////////////////////////////////

using System;
using System.Collections.Generic;

namespace SilverLua.Compiler
{
   internal class BlockState
   {
      private Dictionary<string, Symbol> _values = new Dictionary<string, Symbol>();
      private Dictionary<string, Symbol> _params = new Dictionary<string, Symbol>();
      private BlockState _parentState = null;
      private SymbolTable _symbolTable = new SymbolTable();

      private int _registerOffset = -1;
      
      internal int SymbolCount { get { return _values.Count; } }

      internal BlockState() { }

      internal BlockState(BlockState parent)
      {
         _parentState = parent;
      }

      internal Symbol AddLocal(string name)
      {
         Symbol symbol = new Symbol(this, name, OperandType.Value, _values.Count);
         _values[name] = symbol;
         return symbol;
      }
      
      internal Symbol AddParameter(string name, int index)
      {
         Symbol symbol = new Symbol(this, name, OperandType.Parameter, index);
         _params[name] = symbol;
         return symbol;
      }

      internal Symbol ResolveName(string name)
      {
         Symbol symbol;

         if (!_values.TryGetValue(name, out symbol) &&
             !_params.TryGetValue(name, out symbol))
         {
            symbol = _parentState == null ? new Symbol(null, name, OperandType.NilLiteral, -1)
                                          : _parentState.ResolveName(name);
         }

         return symbol;
      }

      internal void Close(int offset)
      {
         _registerOffset = offset;
      }

      internal int ResolveRegister(int register)
      {
         if (_registerOffset == -1)
         {
            throw new Exception("Cannot resolve symbols to unclosed state");
         }

         return register + _registerOffset;
      }
   }
}
